Fulminant Primary Biliary Cholangitis-Autoimmune Hepatitis (PBC-AIH) Overlap Syndrome in a 27-Year-Old Woman With Childhood-Onset AIH: Steroid-Refractory Decompensation Necessitating Urgent Transplant Evaluation.

Autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC) represent distinct autoimmune liver diseases, each with characteristic clinical, serological, and histological features. Rarely, patients may exhibit an overlap syndrome, presenting diagnostic and therapeutic challenges. We describe a 27-year-old woman with a longstanding history of childhood-onset AIH who subsequently developed clinical and serologic features consistent with PBC, fulfilling the Paris criteria for AIH-PBC overlap syndrome. Despite aggressive treatment with high-dose corticosteroids, she experienced rapid clinical deterioration, developing acute hepatic encephalopathy and requiring intensive care unit admission. A liver biopsy confirmed the coexistence of interface hepatitis (typical of AIH) and florid bile duct lesions (characteristic of PBC). Notably, the patient had a steroid-refractory course, systemic autoimmune comorbidities including ulcerative colitis and pyoderma gangrenosum, and exhibited atypical early-onset disease progression. Ultimately, due to severe and refractory liver failure, she required urgent liver transplantation evaluation. This case highlights the aggressive clinical course and critical management complexities of AIH-PBC overlap syndrome, emphasizing the importance of early recognition, comprehensive histologic evaluation, combined immunosuppressive and cholestatic therapies, and expedited referral for transplantation in refractory cases.